The present invention relates to an optical device, used for, e.g., optical communication or the like, and an optical module provided with the optical device.
Conventionally, an optical device 41 that uses an optical fiber 43 shown in FIG. 5 or the like, an optical device 51 (shown in FIG. 6) described in Jpn. Pat. Appln. KOKAI Publication No. 8-190026, etc. are known as optical transmission-reception devices that are applicable to optical communication, for example.
The optical device 41 shown in FIG. 5 comprises a substrate 42, optical fiber 43, laser diode 44, photodiode 45, filter 46, etc.
The substrate 42, which is formed of a silicon single crystal, is provided with a V-groove 47. The optical fiber 43 is located in the V-groove 47. The laser diode 44 emits signal light beams toward an end face of the optical fiber 43. The photodiode 45 is located over the optical fiber 43. The filter 46 is located dividing the optical fiber 43. The filter 46 guides signal light beams with wavelengths different from the wavelengths of signal light beams that are emitted from the laser diode 44 to the photodiode 45, among other signal light beams transmitted in the optical fiber 43.
The optical fiber 43 of the optical device 41 is connected optically to an optical fiber of an external device such as a connector used for optical communication. In other words, the optical device 41 and the external device are connected optically to each other by means of the optical fibers. Thus, the optical device 41 and the external device can be connected relatively easily, and a loss attributable to the connection is relatively small. In attaching the optical fiber 43 to the substrate 42, moreover, the optical fiber 43 can be positioned with relatively high accuracy with respect to the substrate 42 in a manner such that the optical fiber 43 is fitted in the V-groove 47. Accordingly, the optical fiber 43 that is attached to the substrate 42 can be also connected optically to an optical waveguide of the external device with relatively high accuracy.
In manufacturing the optical device 41, the laser diode 44 and the photodiode 45 must be arranged on or soldered to the substrate 42 in a manner such that the optical fiber 43, which is relatively thin and fragile, is attached to the substrate 42. In some cases, the optical fiber 43 may be damaged during this operation. If the optical fiber 43 is damaged, the volume of transmission of signal light per unit time is reduced, so that the yield of the optical device 41 itself lowers. Thus, the optical device 41 is liable to cost higher.
On the other hand, the conventional optical device 51 shown in FIG. 6 is provided with a planar lightwave circuit 52. A laser diode 53 that functions as a light emitting device, a pair of photodiodes 54a and 54b that function as light receiving devices, and a filter 55 are arranged in predetermined positions on the planar lightwave circuit 52.
The planar lightwave circuit 52 is formed on a substrate 56 that is formed of a silicon single crystal. The lightwave circuit 52 is provided with a core 57 and a cladding 58 that have different refractive indexes. The core 57 and the cladding 58 consist mainly of SiO2 or the like. The paired photodiodes 54a and 54b are connected optically to the core 57 of the planar lightwave circuit 52.
The core 57 and the cladding 58 are formed by a film forming method, such as flame hydrolysis deposition (FHD), chemical vapor deposition (CVD), or physical vapor deposition (PVD).
In this optical device 51, individual waveguides can be formed collectively on the one substrate 56 by the aforesaid film forming method or fine processing technique such as photolithography. Thus, the productivity is high.
In the case of this optical device 51, however, alignment of the respective optic axes of the core 57 and the optical fiber of the external device requires precise adjustment operation. Since the photodiodes 54a and 54b are incorporated in the lightwave circuit 52, moreover, the respective optic axes of the photodiodes 54a and 54b and the core 57 must be accurately aligned with one another. Thus, assembling the optical device 51 requires more labor and time, so that the cost tends to increase. Furthermore, the necessary time and labor for the optical connection of the optical device 51 to the external device also increase.
Accordingly, the object of the present invention is to provide an optical device, which can be produced with improved yield that permits a reduction in cost and can facilitate connection with an external device, and an optical module provided with the optical device.
The optical device of the present invention comprises a substrate having a flat reference surface and a V-groove recessed from the reference surface, and an optical waveguide formed on the reference surface of the substrate and having a core extending along the reference surface.
In the optical device of this invention, the relative positions of the V-groove and the optical waveguide can be accurately maintained by the CVD or other film forming method or fine processing technique such as photolithography. In this optical device, moreover, the core of the optical waveguide is covered by means of a cladding. In attaching or soldering light emitting and receiving devices, which are attendant to the optical waveguide, to the optical waveguide, therefore, the core can be prevented from being damaged. Accordingly, the yield of production of the optical device can be improved, so that the cost can be lowered.
In the optical device of this invention, moreover, the relative positions of the V-groove and the core can be maintained accurately. By fitting, for example, a locating pin of an external device that has an optical fiber into the V-groove, therefore, the respective optic axes of the core and the optical fiber of the external device can be easily connected with high accuracy. Thus, the labor and time required by the connection between the optical device and the external device can be lessened, so that the optical device and the external device can be connected with ease.
In the optical device of this invention, the optical waveguide may be provided with a filter capable of transmitting a signal light beam with a first wavelength transmitted through the core and reflecting a signal light beam with a second wavelength transmitted through the optical waveguide. Preferably, moreover, the substrate is formed of a silicon single crystal and has the V-groove formed by anisotropic etching. According to this invention, the relative positions of the V-groove and the optical waveguide can be maintained more accurately.
The optical device of this invention may be constructed so that it further comprises a light receiving device located on the optical waveguide and a light emitting device for delivering the signal light beam with the first wavelength to the core of the optical waveguide, and that the filter is located on the optical waveguide so as to divide the core of the optical waveguide between first and second portions, and the filter reflects the signal light beam with the second wavelength toward the light receiving device.
In this case, the light receiving device is located beside the optical fiber, so that a photodiode of the plane reception type can be used as this light receiving device. The photodiode of the plane reception type entails relatively low cost, and besides, has a relatively wide light receiving surface, so that it can ease the positioning accuracy that is required when the optical device is provided with the photodiode. These circumstances are advantageous to reduction in cost.
An optical module of this invention comprises a first optical device and a second optical device. The first optical device includes a substrate having a flat first reference surface and a first V-groove recessed from the reference surface and an optical waveguide formed on the first reference surface and having a core extending along the first reference surface. The second optical device includes an optical fiber and a covering portion having a second reference surface extending along the optical fiber and a second V-groove recessed from the reference surface and covering the optical fiber. Further, this optical module is provided with a columnar pin fitted in the first and second V-grooves. The optic axis of the core of the optical waveguide of the first optical device and the optic axis of the optical fiber of the second device are caused to correspond to each other in a manner such that the pin is fitted in the first and second V-grooves.
In the optical module of this invention, the columnar pin is fitted in the first and second V-grooves, whereby the optic axis of the first optical device and the optic axis of the second optical device are substantially aligned with each other. Accordingly, the necessary time and labor for the optical connection between the first and second optical devices are reduced. Thus, connecting operation for the first optical device and an external device, which are optically connected by means of the second optical device, can be carried out quickly and easily.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.